Coast leaving scientists with a sinking feeling

Controversial NOAA report says Louisiana's shores plunging fast — are Texas' next?

By ERIC BERGER--Houston Chronicle

By century's end, much of southern Louisiana may sink into the Gulf of Mexico. The Texas coastline, including Galveston, could soon follow.

That's the sobering — and controversial — conclusion of a new report published by the National Oceanic and Atmospheric Administration that finds the northern Gulf of Mexico is sinking much faster than geologists thought.

The report centers on the humble benchmark, a small metal disk bolted to the ground, that provides a standard elevation above sea level for land surveying and mapping as well as determining flood-prone areas.

But there's one problem with benchmarks: They don't give reliable elevation readings if they're sinking along with everything else.

That's what the geologists who wrote the NOAA report say is happening in Louisiana: The yardstick is broken. Instead of minimal geologic subsidence along most of the Louisiana coast, as previously thought, the state's entire coastal region is sinking at least 5 feet every century.

And although a number of local officials disagree with the report's conclusions about Texas, here's a scary thought: Similar forces could well be at work just a few miles south of Houston.

"Subsidence doesn't stop at the Texas border," said Roy Dokka, a co-author of the NOAA report and a Louisiana State University geologist.

A colleague of Dokka's in Houston, the editor of the Houston Geological Society Bulletin, is more blunt in his assessment of the report. "Galveston," says geologist Arthur Berman, "is history."

Flooding a major threat
The report already has ignited debate in Louisiana. If that state's coast continues to sink, its multibillion-dollar plan to protect coastal cities and wetlands from flooding has targeted the wrong problem, erosion. Every building on land certified as safe from flooding may, in fact, be in danger if Louisiana's benchmarks are flawed. And levees thought to protect New Orleans from a Category 3 hurricane might fail even if a moderate Category 2 storm struck the Big Easy.

Texas could have similar problems if its benchmark elevations are flawed. The National Hurricane Center bases its storm-surge models on benchmarks, as do emergency planners trying to determine when key evacuation routes might flood.

Houston felt the problem acutely during Tropical Storm Allison when benchmarks indicated that certain areas, such as some Texas Medical Center buildings, should not have flooded even in the torrent of rain produced by that storm.

"We know that a lot of benchmarks in Texas are inaccurate," said Gary Jeffress, a mapping specialist at Texas A&M University-Corpus Christi.

Shifting land
Subsidence — the sinking or settling of land — comes in two basic forms. One is man-made, caused by groundwater pumping or oil and gas extraction. The other, which Dokka says is causing nearly all of the problems along Louisiana's coast, is natural, or geologic, subsidence.

Houston has grappled with man-made subsidence for the past 30 years with help from the Harris-Galveston Coastal Subsidence District, which has spent about $10 million studying and measuring the problem.

As a result of this research, the Houston region has undergone a multibillion-dollar conversion from ground wells to surface water for its consumer and industrial needs. In the next decade or so, north and west Harris County will spend as much as $3 billion more for a similar conversion.

Ron Neighbors, general manager of the subsidence district, said he thinks this conversion has largely solved the area's subsidence problems. He attributes little of the region's sinking to geologic subsidence and doesn't think the area's coastal regions may be sinking as much as 4 or 5 feet a century.

"We realize there is some amount of natural subsidence that will occur over time," Neighbors said. "But we believe that to be about three quarters of a foot per century."

If he has little confidence in the report by Dokka, Neighbors has even less in the scientist himself. Neighbors said the Louisiana geologist has incentive to cause fear.

"You don't get any grants if you say everything is OK," Neighbors said.

Berman said that, although conclusions drawn by Dokka's report are controversial, they were checked by NOAA for 18 months and wouldn't have been published if they were bogus. The controversy comes, he says, because the findings challenge existing models.

Every geologist agrees that three main factors contribute to coast loss: rising sea levels, coastal erosion and subsidence. What Dokka and his supporters suggest is that the role of natural subsidence is nearly as important, or even more important, than man-made subsidence. And the problem for coastal planners is that, unlike with man-made subsidence, there's nothing that can be done to stop natural subsidence.

Forces of nature
Dokka and others think geologic forces during millions of years are acting to sink the Gulf Coast. The Texas coast rests upon a mobile layer of shale about 20,000 feet below ground. But because lots of water is mixed in with the shale, it cannot be fully compacted into rock, so it behaves something like toothpaste, geologists say.

A second observation is that several rivers, principally the Mississippi but also the Colorado, Brazos and many others, drain into the Gulf of Mexico, bringing untold tons of sediment over millions of years.

"You're draining almost the entire North American continent into the Gulf," Berman said. "The cumulative weight of that is immense."

So immense, in fact, that the Gulf of Mexico is pushing down on the Earth's crust, making an indent. For coastal regions along the Gulf, it's like being at the edge of a trampoline with a bowling ball weighing down the center: The natural inclination is to slide toward the center. The toothpastelike shale layer facilitates the slide, Berman said. Geologists call it gravity gliding.

Roberto Gutierrez, a geophysicist at the University of Texas at Austin's Bureau of Economic Geology, said Dokka's results were not unexpected among the geosciences community. "The Earth is a dynamic place," he said.

State's efforts fledgling
But even after the Dokka study, the central question — What is the dominant factor driving coastal land loss in Texas? — remains unanswered, he said. Like other geoscientists contacted for this article, Gutierrez said there simply isn't enough data to know how natural subsidence is affecting Texas.

Texas' General Land Office estimates that the state loses about 235 acres of Texas Gulf shoreline each year. Like Louisiana, the state's Coastal Texas 2020 program has focused on coastal erosion.

The coastal program has received funding only since 1999 and has just begun to study the issues, said Lorrie Council, a team leader. During meetings with coastal landowners and public officials, she said, they pointed to beach loss from erosion, primarily when strong storms cause big waves and wash sand out to sea, as the biggest problem.

The state recently created a committee to look at subsidence as a factor, she said.

"It's something we're aware of, but we don't have enough information on it, and we're working actively to get it," she said.

The information may well come from Jeffress, the geographer at Texas A&M-Corpus Christi. Because of efforts by U.S. Sen. Kay Bailey Hutchison, Jeffress says he will receive $665,000 to modernize the height of benchmarks along the Texas coast. He hopes the grant will be renewed annually.

Expensive work
Using a mix of traditional surveying and the Global Positioning System, Jeffress said, he will work with private contractors to begin updating the network of benchmarks installed in Texas shortly after World War II.

It's not cheap. The basic premise of the work Dokka did in Louisiana, which Jeffress will emulate to some degree in Texas, is to start at some point well inland that rests on bedrock. For Dokka that meant the upper reaches of Louisiana. For Jeffress, it means Austin. Then, like traditional surveyors, they take level readings by sight all the way to the coast. It's a time-consuming, costly process, requiring about $1,500 per mile.

One of Jeffress' first tasks, he says, will be checking the seawall road in Galveston and the Gulf Freeway for low-lying spots that could serve as choke points during an evacuation.

He said he has no doubt that many of the existing benchmarks used by highway planners are incorrect. And although it's not his job to interpret why, he says he thinks natural subsidence must play some role.

"I think there's a general trend here," he said. "Considering how many people live along the coast, and how close they live to the water, this could be a problem in the future."

Area well documented
But Neighbors says subsidence in Harris and Galveston counties is the most well studied in the country. Height modernization of benchmarks began here in the mid-1980s, he said, and when communities, including those in Louisiana, wanted to learn how to improve their elevation measurements, they come here.

The subsidence district's records, he said, indicate that subsidence has slowed or even halted in Harris and Galveston county areas where groundwater pumping has ceased.

To justify billions of dollars in conversion from groundwater to surface water, he said, the science had to be sound.

Simply put, Neighbors said, if natural subsidence were a problem here he would know about it. Then he paused, in thought. Geology, with all of the Earth's chaotic, unpredictable and violent processes, is not a science of absolutes.

"I'm not going to say that we've learned it all," he added. "We don't know everything. But I don't think we're going to fall into the sea anytime soon."

If you're interested, I can post the link to the pdf so you can read and evaluate Dokka's report without spin.

Essentially what Dokka did was evaluate all of the benchmarks in Louisiana by tying the surveys to areas not thought to be either actively sinking or emerging. He then looked at the rates of subsidence of teh historical benchmarks and compared them with the most recent survey. He also confirmed these data with kinematic surveys of the area. All of them converge to the common conclusion that he presents.

You would not believe the turff fighting that is going on right now because of Dokka's report. Some folks in my agency think he's a complete waste of time, which I believe is in no small measure due to envy. IMO Dokka has firmly shot the ball into the court of everybody who doesn't agree with him. IOW, Dokka did a heck of a lot of homework and just on the amount of data analyzed, now holds the best model of coastal subsidence for LA. That is for his detractors to disprove.

Bot

(Full disclosure, I know most of these guys. We're talking big egos here).

Don't worry about it Bot you people are getting so much sediment from Montana and North Dakota from the Missouri river system that you will be able to bury your dead below ground in a few years.

__________________
1983 300-D turbo
1985 300-D turbo
1959 Harley Panhead chopper
1929 Ford coupe restored
I hang out with Boneheaddoctor at Schuman Automotive OBK#5
All liberals are mattoids but not all mattoids are liberal.

That be some hairy stuff. I guess the only constant is change but I always thought noticeable changes in coastlines (as in hundreds of yards or more) would happen over many lifetimes, not just one or two.

I'm not hoping to find a human cause here, but if all of Dokka's conclusions were correct about the bowling ball in a trampline effect, wouldn't this have been going on for the last few hundred years that people have been keeping track of these things? I gather that the rate of change has sped up dramatically. If this is true, I'm wondering if there isn't a man-made element that has contributed to that.

__________________
1986 300SDL, 362K
1984 300D, 138K

Unfortunately, the Corps of Engineer's first priority is maintaining shipping channels. The way the maintain the channels is by constricting flow through teh southwest pass which dumps sediment off the continental shelf.

Someday that could become a problem. See, there's this function called, "angle of repose'. Like when you pour dry salt into a cone it seeks an angle relative to the size and shape of the grains.

Well, the angle of repose of fine sands and silts deposited off the shelf is tremendously out of equilibrium, due to over a century of artificial channel maintenance. Sometime it will regain equilibrium by shifting several cubic miles of sediment down slope. That will displace an equal volume of water. The water will move away from the slump area in a large-volume wave.

And flood control... prevents fresh top silt from inching the land up periodicly.
I had always heard New Orleans was a city of legendary fame but it would seem to be marching toward an Atlantian status that I did not suspect.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

There is evidence in support of your thesis. Until the LMV (Lower Mississippi Valley) was levee'd, silt, sand and nutrients were lifted from the bed and epsoited far and wide across the delta regions of AR, MS, and LA. Sometimes creating a seasonal lake a couple hundred miles acroos and replenishing the soul. The last flood that I saw was in 1983/1984 during which the Corps of Engineers ordered the abandonment of the flood control structure at Old River. I was in Concordia Parish running trot lines with some friends. We took teh boat into some strange areas and placed trot lines and yo-yo's on the edge of roadways, the roads under 3-6 ft of water.

But with leveeing, the nutrients and water are forced off the continental shelf rather than down the distributary system consisting of Bayou LaFourche, Bayou Teche, the Atchafalaya River, etc. By forcing down a single channel, the carrying capacity (or whatever they call it) of the river stays high because of the constriction. If there were no levees, especially on the west bank, the water would roll over the countryside and slow down. Slow water cannot hold as much stuff in suspension as fast water, so silt would fall out in proportion to the relative velocities. It used to pass down the distributaries in huge sheet flows through the swamp, gradually building land in the swamps and carrying the sediment to the near-shore environment for deposition of fines in the near shore. This is where the marsh and barrier islands get replenishment. Since the river has been levee'd for over 100 years, the marsh and barrier islands have been deprived of sedimentation and nutrients. One consequence of that is accelerating land loss. For in an erosion environment, if sediment doesn't come in and replenish what is lost, the loss rate accelerates.

If I read this right (and I'm an inlander, so I'm largely iggorant about levies and the like) building levies and maintaining a good shipping lane has the advantages of way reduced flood damage and commercial shipping but possibly the disadvantage of eventually losing some of what one was trying to protect with the levy in the first place.

Damn, I hate it when that happens.

__________________
1986 300SDL, 362K
1984 300D, 138K

That's about it in a nutshell.

There are other factors involved in land los in LA, too. Petroleum extraction causes a very local land loss, some (extreme) sites subsided a couple of feet in a year or so over several hundred acres. You can look through the water and see marsh grasses below. But this is not a common phenomenon and is pretty local. Also all of the canals built for access to the Gulf and inland waterways allows rapid movement of saline water into fresh marshes, which quickly kills fresh marsh vegetation. This phenomenon is ubiquitous in S. LA and parts of TX. And of course, the whole coastline is subsiding and not being replenished by overbank flooding of the MS River. Oh yeah, there's also the sea level rise as a result of melting snowpacks and glaciers. The combined effect is a huge rate of landloss, on the order of acres per hour if looked at linearly since the 1950's. (But it is not linear, it proceeds in a downward stairway fashion because local events work with subsidence).

It is hugely complicated. But the whole problem may solve itself naturally. Either through massive spring floods overwhelming the flood control system of a Cat 5 hurricane slowly moving up the MS to NOLA and Baton Rouge. That's when we'll enjoy the TV spectacular of 10's of thousands, perhaps hundreds of thousands of people dying. Then we'll all wring our hands and wail our laments and blame politicians for not doing something.

i really don't think i am gonna miss TX.. the faster the better... hehehe

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72 W114/M130

RedMeat cartoon

I have a feeling that all the concerns about over-population will eventually be laid to rest in natural solving as well. To the many millions and perhaps billions who would starve, like the proverbial rabbits on an island w/o predators, it will surely be unpleasant, tragic, etc. but I suspect Mother Nature and God will look on impassively. They've seen it before and are perhaps not likely to suffer fools lightly.

BTW, I wanted to thank you for the post about the mathematics of tile patterning. Interesting stuff, I bookmarked it. I don’t know if you saw one post where I mentioned I was about ¾ of the way to a math degree. BHD had accused me of being a liberal arts major (shudder) and I couldn't let that kind of slander go by uncorrected.

I’m thinking maybe to retire as a high school math teacher. I had a really good one in high school and I’d like to repay the debt. Now if I can just remember the finer points of Newton’s method for deriving the zero roots of a complex polynomial. I wrote a computer program (Pascal) in ’85 which successfully ran that formula and I can barely remember how it goes.

BTW, I heard an interview with Christopher Hitchens about his new book on Jefferson on our local NPR station’s "Forum" talk show, one of the better ones I’ve heard. Audio transcript available at:

http://www.kqed.org/epArchive/R506061000

Krasny, the host, looks a bit like a cocky a$$ in the picture on the website but he's solid, IMO. Hitchens is a fascinating fellow. I don’t see eye to eye with him on all matters, but his speaking and thinking are clearly worth paying attention to. You once mentioned him “slaughtering” Chomsky. While I, of course, find that highly implausible , I would be interested in examining the evidence. Was it a TV debate or written duel?

__________________
1986 300SDL, 362K
1984 300D, 138K

When I took my current position I remembered enough math that I knew I needed help and quick to get the discipline of mind back into the groove. I am no mathematician, but I use math a lot. Sort of like a plumber uses pipes but is not a mechanical engineer. But the analytical discipline need froo (and IMO developed by) mathematics is really essential if you want to use the tools effectively. So I took an intro calculus course (been 20 years or so since I'd had a math course). I worked my ever-lovin' ass off. I worked every homework problem in the book and every one in a Schaum's outline and it was the only course I took. I got by with a solid "B". Don't even THINK about grade inflation B, either. taking the course and passing it gave me confidence to use the tools available in Mathematica. If you like mathematics and think graphically, Mathematica will sweep away all the comuter games you've ever bought. The graphing of functions is just plain amazing. Anyway, if you're thinking about going back into math, take a course at a local JuCo and buy Mathematica.

Concerning the Chomsky/Hitchens debate, it was carried out in "The Nation", for which Hitchens used to write. I'm sure if you Google the two names together you'll get a bunch of links to the letters. I used to read the Nation when Hitchens was there, but more or less quit reading it when he left.

Christopher Hitchens and his brother Peter, were both atheists and communists of the Trotsky school. Both are now columnists though Peter stayed in England and writes a column for the "Telegraph (I think, perhaps one o fthe Englishmen on the Forum knows). Anyway, Peter had got religion (I think Roman Catholicism) and became a stalwart Thatcherite. Christopher is still a bit of a commie and firmly an atheist. Mostly Christopher is as he self-describes, a "Contrarian". He sticks a wet finger in the wind and fights for the opposite side of where people think he would be. But even that is inconsistent, because he'll also embrace the notions of the left that are (IMO) wacky.

He hates Kissinger.
He wrote a book about the evils of Mother Teresa.
He loves baiting people of any religious persuasion whatsoever. Including supporters of the Dali Lama (who he calls a religious dictator without a country).
And much more. Sort of a commie Mark Twain.

So, here's Chomsky, the intellectual darling of the far left. he's smart and erudite. He has great academic credentials. He writes to The Nation that the USA more-or-less deserved the 9/11 attack.

Hitch demures.

Foodfight begins.

Bot

I'm gonna check that out. Sounds like my kind of food fight.

BTW, I just saw this item on my NYTimes on line thing -- comes to my e-mail, imagine that -- they have a "quotation of the day" feature and here it t'was:

"If we don't get light back to the plants on the bottom she'll be a giant muck hole. She could be dead this time next year."
SUSAN BAKER, campground manager for Okeechobee County, on the Lake Okeechobee ecosystem.

(!?!) I did a yahoo search on the lake and got a bunch of feel good, "Ya'all come see us now, y'heah!" kind of sites. I'm going to do some more searching later.

I can't imagine that you've heard anything about this....

__________________
1986 300SDL, 362K
1984 300D, 138K

I don't know about Okeechobee per se, but in any nutrient rich aquatic system if it becomes light-limited, you get a huge build-up of inorganic nutrients, oxygen depletion, and then anaerobic decomposition. Once things go anaerobic it kills all aquatic life that can't go elsewhere. Then it becomes extremely smelly.

...Hitchens found Imperialism to his liking and the taste of blood too sweet to go back and reconcile his former belief system.

I believe Mr. Clemens was sympathetic to commie causes and emphatically anti-imperialist.